1. Field of the Invention
The present invention relates to optical technology, and more specifically relates to a multipurpose testing device for use in testing various parameters relating to optical cross connect switching devices.
2. Description of Related Arts
Communication technology has progressed significantly in the past few years. Today, much information is carried over optical communications fiber. This technology, known as fiber optic technology, allows for the transport of information at data rates currently exceeding billions of bits of information per second. Part of the technology that enables this optical communication is the ability to direct light onto an optical fiber and switch that light appropriately. For example, it is desirable to provide the ability to switch an optical signal from one optical fiber to another optical fiber. In recent years there have been extensive efforts to develop commercially viable optical switches.
Presently there are a variety of different types of optical switch architectures available on the market. One proposed optical switch architecture contemplates the use of arrays of Micro Electro-Mechanical Systems (MEMS) mirrors to accomplish the switching. An example of such an optical switching system is described in U.S. Provisional Patent Application No. 60/088,075, filed on Jun. 6, 1998, naming Herzel Laor as inventor (also published as International Publication Number WO 99/66354), the entirety of which is incorporated herein by reference for all purposes.
FIG. 1 shows a block diagram of a conventional photonic cross connect optical switching system configuration 100 which may be used for switching, in the optical domain, optical signals received on any of the input ports 102 to any desired output port 104. As shown in FIG. 1, the optical cross connect system 100 includes an optical cross connect or switching device 110 which includes a plurality of input ports 102 configured to receive a plurality of different optical signals via input fibers 103. The optical cross connect device 110 also includes a plurality of output ports 104 for providing output optical signals on output fibers 105. The optical cross connect device 110 is used to provide optical switching capability in order to optically couple an optical signal from any desired input port 102 to any desired output port 104. Thus, for example, the optical cross connect device 110 may be configured to couple, in the optical domain, input port 102a to output port 104c to thereby optically switch optical signals on input fiber 103a to output fiber 105c. 
It will be appreciated that the optical cross connect device of FIG. 1 corresponds to a photonic optical switch which is configured to switch optical signals in the optical domain rather than in the electrical domain. Manufacturers and users of photonic optical switching systems such as that shown in FIG. 1 will periodically have the desire to verify that the photonic cross connect device is functioning properly. For example, a manufacturer of a photonic optical switch may desire to perform path verification of the switching device by verifying, for example, that a selected input fiber is optically connected only to a desired output fiber, and that no portion of the input optical signal is detected on any other output fiber except the desired output fiber.
Currently, there is only a limited selection testing equipment available on the market for testing and verifying the different functional aspects performed by photonic optical switches. FIG. 2 shows an example of a conventional testing system configuration which may be used to test various aspects of an optical switching system such as that illustrated in FIG. 1. As shown in the example of FIG. 2, two optical switch testing devices 120a and 120b are used to verify the cross connect connectivity between selected input fibers 103 and selected output fibers 105. Such conventional testing equipment may be provided by manufacturers such as, for example, Anritsu Corporation of Japan, and Agilent Techologies, Inc. of Palo Alto, Calif.
According to conventional techniques, in order to verify the optical cross connect connectivity between a selected input fiber and a selected output fiber, a first testing device 120a is optically coupled to a selected input fiber (e.g. 103a) and a second testing device 120b is optically coupled to a selected output fiber (e.g. 105a). A test optical pattern is then transmitted by the first testing device 120a on input fiber line 103a. A first aspect of the cross connect connectivity verification check is performed by detecting whether the test optical pattern (sent by testing device 120a on input line 103a) is detected on output line 105a. The second testing device 120b is therefore connected to the output fiber 105a in order to detect the presence of the test optical pattern.
Assuming that the test optical pattern is detected on the desired output line 105a, a second aspect of the cross connectivity verification test is performed by verifying that the test optical pattern is not detected on any other output fiber except the desired output fiber 105a. In order to accomplish this second aspect of the cross connectivity verification test, testing device 120b must be manually coupled to each individual output fiber 104a-n in order to test for the presence of the test optical pattern. However, it will be appreciated that such a testing scheme is labor intensive, and may require a significant amount of time to complete. Moreover, as the number of input fibers and output fibers increase, the length of time needed to perform conventional cross-connect verification testing increases exponentially, and eventually becomes an impractical and unworkable task.
An alternative solution is to provide a separate testing device on each input fiber and/or output fiber in order to reduce the time required to perform the cross connect verification testing. However, currently the cost of conventional optical switch testing devices range, for example, from $200,000 to $500,000 for each piece of testing equipment. Accordingly, a solution which calls for multiple testing devices may prove to be cost prohibitive.
In light of the above, it will be appreciated that there exists a continuing need to improve upon optical switch testing technology.